Broadly, the LTE communication network architecture involves at least one User Equipment (UE), at least one eNodeB (eNB) and Evolved Packet Core (EPC) nodes (comprising of various functional elements such as Mobility Management Entity (MME), Packet Data Network Gateway (PGW), Serving Gateway (SGW), Home Subscriber Server (HSS), Policy and Charging Rules Function (PCRF), and so on). An Application Server (AS) could also be a part of the network architecture, connected to the EPC (to the PGW) over the SGi interface using a wired link. The AS controls and coordinates communication amongst the UEs.
For the purpose of certain types of public safety applications, which demand rapidly deployable systems, a large and complex system comprising of multiple entities in the EPC/core, network might not be suitable. Also, several applications of public safety networks do not require the public Internet for operation, or are required to be deployed in remote regions which do not have an existing infrastructure, while providing connectivity only among the users of the service, typically over a local region.
Considering a case where the eNB fails, UEs would be cut-off from the AS and this could result in disruption of the network operations. As the eNB serves as the primary communication anchor for the UEs to connect to the EPC and AS, high availability of the eNB is very crucial for mission critical applications.